1. Field of the Invention
The present invention relates to the treatment of gynecological cancers, and more specifically to radiation delivery devices for insertion into a patient""s vagina and cervix.
2. Description of Related Art
Approximately 70,000 women every year in the United States are diagnosed with an invasive gynecologic malignancy. Of this group of tumors, roughly ⅓ receive radiation as part or all of their treatment. In a majority of the patients treated with radiotherapy, the placement in the body of low-dose-rate radioactive sources (brachytherapy) is utilized to maximize control of the cancer while minimizing long-term normal tissue complications from such treatment.
Traditionally, women with gynecologic cancers have radiation therapy as all or part of their treatment. A major portion of their radiotherapy involves the loading of radioactive materials into special applicators that are surgically placed into the patient""s vagina. For approximately forty years, the delivery system utilized for low-dose-rate brachytherapy of patients with cancers of the cervix has involved vaginal colpostats (ovoids) and an intra-uterine tandem. Several drawbacks of this system include the inability to deliver sufficient radiation dose to treat tumors involving both the cervix and mid to lower portions of the vagina during the duration of the application. The vaginal ovoids must be replaced by the insertion of a tandem and vaginal cylinder with or without the placement of transperineal radioactive sources into the para-vaginal tissues (interstitial implantation), in order to treat this distal vaginal disease. A separate implant procedure from the initial cervical treatment is usually required under anesthesia, followed by a separate subsequent hospital stay for the duration of this brachytherapy application. Thus, there is increased risk of morbidity and mortality from this second implantation of sources in addition to the increased costs arising from a second hospitalization.
Another problem associated with conventional tandem and ovoid application systems is the requirement of ovoids stabilization during the implant procedure. Stabilization is usually effected by intra-vaginal packing of gauze by the radiation oncologist to prevent movement of the ovoids once in place. Due to physician error during the implant attempt or to narrowing of the vaginal apex from the previous external beam irradiation, the vaginal ovoids may not rest directly in contact with the cervix, thereby resulting in dose inhomogeneity and increased risk of tumor persistence or recurrence. Again, a vaginal cylinder is often used instead of ovoids to complete the brachytherapy procedure. However, typical vaginal cylinders do not deliver sufficient radiation dose to the prescription points of interest for cervical cancer, without significantly increasing the risk of vaginal injury, ultimately resulting in a reduced likelihood of achieving long-term patient survival.
Postoperative radiotherapy of patients having cancer of the endometrium utilizes conventional vaginal ovoids or cylinder if the patient is at risk of tumor recurrence at the vaginal apex or lower aspects of the vagina, respectively. However, should both the apex proximally and distal regions of the vagina be at risk, two separate procedures would be needed to achieve adequate radiation dosage to the entire vagina without increased toxicity.
Attempts have been made to solve these problems. U.S. Pat. Nos. 4,244,357 and 5,947,891, for example, disclose typical apparatus and methods for treating patients with cervical cancers. In these patents, the tandem, which contains the radioactive sources, is inserted into the vagina, and two ovoid half-cylinders are used as spacers around the tandem. The two half-cylinders disclosed in these patents are locked together with various interlocking mechanisms. In the devices taught by these two patents, the tandem is the sole radiation source.
In U.S. Pat. No. 4,554,909, the typical ovoid half-cylinders are replaced by a single, contiguous cylindrical structure. This cylindrical structure may reduce the need to pack the vagina with gauze to stabilize the device, and includes cavities for housing radioactive sources. However, in the device taught by this patent, the cavities provided to house radioactive sources are metal, and these metal cavities are connected to a metal loading tube. The presence of these metal structures within the cylinder causes an inhomogeneous radioactive dose distribution. Additionally, the disclosed design provides neither rectal nor bladder shielding.
Therefore, a need exists for an improved multicomponent application system for delivering low-dose brachytherapy to cancerous tissue in patients.
The inventive multicomponent vaginal cylinder system for low-dose-rate brachytherapy is ideal for addressing each of these problem areas without compromising the delivery of homogenous radiation dose to treat patients with malignant gynecologic tumors. Utilizing low-dose-rate gynecological brachytherapy, it is physically impossible to combine tandem, vaginal cylinder and ovoids in one implantation attempt to deliver a homogeneous dose to both the ectocervix/vaginal apex along with the remaining lower vagina via a traditional Fletcher-Suit-Delclos applicator system. This is because the typical ovoids have hollow steel handles that extend outside of the patient""s vagina, blocking the insertion of a standard vaginal cylinder. The inventive multicomponent vaginal cylinder system overcomes this drawback, and allows such combined treatment.
A preferred embodiment of the invention is a multicomponent vaginal cylinder system comprising a tandem configured to house at least one radiation source, a vaginal cylinder structure, and one or more removable ovoid cartridges. The vaginal cylinder structure has a tandem slot into which the tandem can be inserted so as to be slidably engaged with the vaginal cylinder structure, one or more hollow cartridge spaces, and a proximal flared portion constructed and arranged to abut patient tissue. The removable ovoid cartridges are constructed and arranged to house at least one radiation source and to be inserted into the hollow cartridge spaces of the vaginal cylinder structure.
The tandem slot may be centrally positioned within the vaginal cylinder structure. Once the tandem is inserted into the slot, it may be fixedly engaged by means of a fastener, such as a set screw.
The removable ovoid cartridges may include generally cylindrical cavities for the storage of radioactive sources. These cavities may be forwardly positioned at proximal ends of the cartridges, and may extend perpendicular to a long axis of the removable ovoid cartridges.
The hollow cartridge spaces of the vaginal cylinder structure extend parallel to a long axis of the vaginal cylinder structure, and may extend through a substantial portion of the vaginal cylinder structure, generally from openings in a distal surface of the vaginal cylinder structure to an interior wall formed at the origin of the proximal flared portion of the cylinder structure. The removable ovoid cartridges may be fixed within the vaginal cylinder structure by a fastener.
The vaginal cylinder structure itself may be molded from a biocompatible plastic, and optionally, the biocompatible plastic may be transparent. In general, the vaginal cylinder structure is designed to be disposable.
The vaginal cylinder structure may also comprise radiation shielding extending over at least a portion of the proximal flared portion. This radiation shielding may be, for example, steel plate constructed and arranged to be attached to the proximal flared portion.
Another preferred embodiment of the invention is a vaginal cylinder structure having a proximal flared portion; the vaginal cylinder structure comprising a tandem slot extending through the entire length of the vaginal cylinder structure; one or more removable ovoid cartridges capable of housing at least one radiation source; one or more hollow cartridge spaces, each capable of housing an ovoid cartridge; and optionally, removable radiation shielding. The vaginal cylinder structure may comprise a tandem slot centrally positioned within the vaginal cylinder structure. The one or more removable ovoid cartridges may comprise one or more radiation sources. These one or more radiation sources may be forwardly positioned at proximal ends of the removable ovoid cartridges. The vaginal cylinder structure may be molded from a biocompatible plastic, and optionally, a substantially transparent biocompatible plastic. Such plastic vaginal cylinder structures may be disposable.
A method of treating a gynecological cancer comprising inserting a tandem housing one or more radiation sources into a patient""s vagina such that the tandem extends from a contact point within the patient""s body exteriorly through the patient""s vagina; inserting a vaginal cylinder into the vagina such that the tandem is situated within a tandem slot of the vaginal cylinder structure and the vaginal cylinder structure surrounding the tandem proximally abuts cervical tissue; and inserting one or more ovoid cartridges capable of housing one or more radiation sources into hollow cartridge spaces of the vaginal cylinder structure positioned adjacent to and extending in parallel to the tandem, thereby irradiating targeted tissues to treat a gynecological cancer. The vaginal cylinder may comprise radiation shielding for protecting non-target tissues from irradiation. The shielding may comprise steel-type shielding.
The method may further comprise afterloading one or more radiation sources into proximal ends of the one or more ovoid cartridges prior to insertion into the hollow cartridge spaces of the vaginal cylinder. The one or more radiation sources may be employed via this method to deliver radiation to at least one target tissue selected from the group consisting of ovarian, vaginal, uterine and cervical tissue. In particular, malignancies of the uterine cervix and endometrium may be treated via the inventive multicomponent vaginal cylinder system. Preferably, the one or more radiation sources comprise Cesium-137.